title: Attenuation of S-T segment elevation during repetitive coronary occlusions truly reflects the protection of ischemic preconditioning and is not an epiphenomenon.
abstract: Attenuation of S-T segment elevation between the first and subsequent balloon inflations of a coronary angioplasty procedure has been assumed to indicate a transition to a preconditioned state, but there has been no validation of this assumption. Open-chest rabbits were instrumented with a coronary snare and epicardial electrode. The coronary artery was occluded twice for 5 min with each occlusion followed by 10 min of reflow before a final 30 min occlusion. The evolving S-T elevation was quantitated as the voltage-time integral. For the first coronary occlusion total S-T segment elevation averaged 40.8+/-5.4 mV x min, significantly greater than 26.2+/-4.6 mV x min for the second occlusion (p < 0.001). There was no further change during the initial 5 min of the third occlusion (24.5+/-4.5 mV x min). When the protection of ischemic preconditioning was blocked by intravenous infusion of 8-(p-sulfophenyl)theophylline, an adenosine receptor antagonist, attenuation of S-T segment elevation was no longer apparent. When preconditioning was pharmacologically triggered by tyramine rather than ischemia, there also was no alteration in S-T segment elevation among the 3 occlusions. Therefore, S-T elevation was diminished during the second episode of ischemia only when a transition occurred from non-preconditioned to preconditioned state between occlusions. An attenuated S-T segment is a valid marker for the presence of the preconditioned state.
authors.affiliation: Department of Physiology, University of South Alabama, College of Medicine, Mobile 36688, USA.
authors.forename: M V
authors.initials: MV
authors.lastname: Cohen
authors.forename: X M
authors.initials: XM
authors.lastname: Yang
authors.forename: J M
authors.initials: JM
authors.lastname: Downey
mesh_terms: D000818:Animals; D003327:Coronary Disease / Q000503:physiopathology*; D004562:Electrocardiography; D006439:Hemodynamics / Q000187:drug effects; D007275:Injections, Intravenous; D019157:Ischemic Preconditioning, Myocardial; D009203:Myocardial Infarction / Q000503:physiopathology; D011817:Rabbits; D015424:Reperfusion; D013806:Theophylline / Q000008:administration & dosage / Q000031:analogs & derivatives; D014439:Tyramine / Q000494:pharmacology
chemical_list: C031433:8-(4-sulfophenyl)theophylline; D013806:Theophylline; D014439:Tyramine